It's certainly not my intention to start a Nikonian brawl, but this real-life example (unlike diagrams and lab tests) actually seems a tiny bit more noisy than what I would've expected. If I was asked to guess, I would certainly think it's much higher than ISO 3200 - by at least a stop. It might be due to post-processing perhaps?

In my opinion and based on what I see in the pictures Df is clearly better than d800 or Canon 7D in following pictures. The first is from Df, second from d800 and the third one from Canon D7. Df pictures are taken in worst light condition, but in spite of that In shadow areas there is least noise in Df pictures. Df and d800 are iso 1600 and Canon is iso 640!. All pictures are taken in raw and converted with raw converter. In Df picture Lightroom noise reduction is 0, but In d800 and Canon pictures luminance Nr must have been used. This is unfair comparison

Not unfair - completely useless! You can't seriuosly compare images taken on different dates in different conditions! And are we looking at 100% crops here or the more realistic same image size? A meaningful comparison has to be controlled if you want to make any conclusions from it!

to Df but it shows how good the sensor of D4 / Df is.

It is a great sensor (I have a D4), but the comparison here is not really useful!

Is it completely useless? Really? I think it is not from my point of view. This is not a scientific test, and not 100% reliable. Nobody has said that. But I know what I see and have seen from d800, D3, Canon 1dmk2 and 3, 5 dmk2 in different situations. I like Df and it´s sensor and also it´s af and that is the point here.